Transistors are designed to operate over a wide variety of conditions depending on the application. In many applications, the transistor is the limiting factor on the performance that may be obtained in a system. Also, the transistor may contribute significantly to the overall power dissipation or efficiency of the system.
In general, increasing the transistor power density is one path to increasing device performance. Increasing the power density of a transistor reduces the size required to deliver a predetermined power level. Typically, a making the physical size of the die smaller results in corresponding reduction in device parasitics. Higher switching frequencies, higher operating frequency, and/or wider bandwidth are examples of increased performance of the transistor. On-resistance per unit area also decreases due the increased packing density of transistors. Increasing the number of devices that may be manufactured on a wafer may also result in a reduced cost of manufacture. However, increasing power density cannot be at the expense of device breakdown voltage or effective removal of heat away from the transistor.